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mercredi 4 septembre 2019

Eye Manifestations of Intrauterine Infections


Introduction
The most common congenital infections are summarized by the mnemonic TORCH: Toxoplasma gondii, Others, Rubella, Cytomegalovirus, and Herpes simplex virus. “Others” includes treponema pallidum, varicella–zoster virus,Epstein–Barr virus,human immunodeficiency virus, and lymphocytic choriomeningitis virus.There is an additional “other,”namely West Nile virus. These are all agents that produce a relatively mild illness in the mother.More virulent agents result in a spontaneous abortion or stillbirth. They are transmitted transplacentally,and have a direct toxic effect. Additionally, in the first trimester, when the fetus has immature, developing organs,there may be a teratogenic effect. Diagnosis can be made by elevated levels ofIgM and IgA antibodies,and if the fetus is unable to eliminate the organism,this may lead to chronic infection and immune tolerance.
13.2 Toxoplasma gondii
13.2.1 Agent and Epidemiology
Toxoplasma gondii derives from the Greek,toxon meaning bow (the shape of the proliferative form), and gondii, for a rodent (Ctenodactylus gundi) indigenous to North Africa from which the organism was first isolated [55].Toxoplasma
gondii is an obligate intracellular parasite, which probably evolved from a unicellular alga since it has an organelle similar to a chloroplast. It has a life cycle that has three forms,an oocyst (found in the gut of cats), a tissue cyst, and an active, or proliferative form. The source to humans includes cat feces, in which the oocyst may be infective for up to 1year in warm,moist soil,and raw meat,in which the tissue cysts are viable. The prevalence in humans varies with age, under 5years, the antibodies are found in less than 5% of the population, while over 80years,they are present in 60%. Seventy percent of the obstetric population have negative antibodies,and is at risk for transmission to the fetus [40].The risk of passage to the fetus and the severity of the infection are affected by the gestational age at the time of maternal infection.Transmission to the fetus is 25% in the first trimester, 75% in the third trimester,and over 90% in the last few weeks of pregnancy.The severity of the fetal infection is inversely related to gestational age,with the earlier infections being the most severe [23,61].
13.2.2 Diagnosis
The diagnosis is made by multiple methods including ELIZA for IgM and IgA.It is important to test undiluted samples, because the serum levels may be very low in eye disease.The workup includes a CBC,with differential and platelet levels,and a CT scan looking for hydrocephalus and intracranial calcifications especially in the periventricular regions.
Eye Manifestations of Intrauterine Infections Marilyn Baird Mets,Ashima Verma Kumar
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13.2.3 Systemic Manifestations
The systemic manifestations are the classic triad of chorioretinitis, hydrocephalus, and intracranial calcifications.Ninety percent of neonates are asymptomatic;however,they can show a continuous clinical spectrum including: abnormal cerebrospinal fluid,anemia,seizures,intracranial calcifications, jaundice, fever, hepato splenomegaly, hydrocephalus, microcephalus, retardation,vomiting,and diarrhea [42,70].
13.2.4 Eye Manifestations
Eighty-five percent of patients with subclinical congenital infections are reported to develop chorioretinitis [70]. The eye manifestations of congenital toxoplasmosis found in a large study are summarized in Table13.1 [48].
Anterior Segment. Microcornea was seen in 19% of patients and cataracts in 10% [49]. It should be noted that these were never isolated findings and that they were always seen in association with posterior segment disease.
Retina. The most common eye finding in patients with congenital toxoplasmosis is chorioretinal scars,which were present in 79% of the patients. The classic location is the macula (Fig.13.1); however, the most common location was in the periphery (64%).If you consider the total surface area of the retina,there was a predisposition for the macular area (58%).In addition,active retinitis was seen in 11% and retinal detachment in 10% [49].
Optic Nerve. Optic atrophy was present in 20% of patients with congenital toxoplasmosis [49].
Microphthalmia and Phthisis. Microphthalmia and phthisis were reported in 13% and 4%,respectively [49]. Visual acuity ranges from 20/20 to 20/400 in the presence of macular lesions, the better vision being unexpected [49]. Therefore, pre
206 Chapter 13 Eye Manifestations of Intrauterine Infections
Table13.1. Ophthalmology manifestations of congenital toxoplasmosis
Diagnoses of patients Percentage of patients checked with findings
Chorioretinal scars 79 (74) Macular 58 (52/89) Juxtapapillary 52 (46/89) Peripheral 64 (57/89) Strabismus 33 (31) Nystagmus 27 (25) Optic atrophy 20 (19) Microcornea 19 (18) Microphthalmos 13 (12) Retinitis (active) 11 (10) Cataract 10 (9) Retinal detachment 10 (9) Vitreitis (active) 5 (5) Phthisis 4 (4)
Numerator represents number of patients with finding; denominator is the total number, unless otherwise specified. Patients with bilateral retinal detachment in whom the location of scars was not possible were excluded from the denominator. Number in parentheses is total number of patients with findings
Fig.13.1. The right eye of a 25-year-old white male with a history of congenital toxoplasmosis. Vision recorded at this exam was 20/80. The slide shows a characteristic “toxo”lesion of the macula with areas of significant atrophy in which both choroidal vessels and sclera are visible
dicting future vision in a preverbal child should be done with caution. Of the patients followed from the newborn period and treated,29% had bilateral visual impairment with the vision in the better eye being less than 20/40.Causes for this visual impairment in eyes with quiescent lesions included macular scars,dragging of the macula secondary to a peripheral lesion,retinal detachment,optic atrophy,cataract,amblyopia, and phthisis. Recurrences were seen in 13% of treated patients, and 44% of untreated historical patients, and occurred contiguous to old scars, but also in previously uninvolved retina.This latter finding is consistent with the fact that toxoplasmosis cysts have been demonstrated in mouse retinas,with no disturbance of the retinal structure, thus on ophthalmologic examination would appear normal [10]. Recurrent infection can result in further loss of vision, especially if they occur in the macular area.
13.2.5 Treatment
Treatment is triple therapy with pyramethamine, sulfadiazine, and leukovorin [47]. Leukovorin (folinic acid) should always be administered in conjunction with pyramethamine to provide for the synthesis of nucleic acids by the human cells. Monitoring by CBC and platelet counts weekly is required because ofthe possible, reversible bone marrow suppression from the pyramethamine. In spite of these required precautions, this therapy can be used safely in very young infants for extended periods of time.
13.2.6 Prevention
Prevention includes avoidance of raw meat and cat feces (changing cat litter boxes and gardening) during pregnancy.If a pregnant woman is known to contract toxoplasmosis during her pregnancy,treatment with spiramycin decreases the possibility of passage of the organism to the fetus [17, 22, 23]. Spiramycin has no known
teratogenic effect.Later in gestation,if the fetus is known to be infected,treatment with pyramethamine and sulfadiazine is appropriate [17–19, 36].
13.3 Rubella Virus
13.3.1 Agent and Epidemiology
The rubella virus is a member of the Togaviridae family in which the virus contains a single-stranded RNA surrounded by a lipid envelope, or “toga.” The congenital form was first described by an ophthalmologist, Sir Norman McAlister Gregg in 1941. He practiced in Sydney,Australia,where he reported several cases of congenital cataracts, congenital heart disease, and deafness associated with rubell a during pregnancy [31]. This represents the first demonstration of teratogenicity secondary to a viral agent.Rubella has worldwide distribution,and is a major cause of blindness in developing countries.However,it is rare in the United States since its epidemic pattern was interrupted in 1969 by widespread use of the vaccine [3].
13.3.2 Transmission
Transplacental infection occurs during the viremic phase in the mother, resulting in fetal viremia. The incidence of congenital infection is dependent on the month of gestation during exposure, with it being 90% in the first 11 weeks, 50% during weeks11–20, 37% during weeks 20–35, and 100% during the last month of pregnancy. However, the rate of congenital defects is 100% in the first 11weeks, 30% in weeks11–20,and none after that.Interestingly, cataracts and glaucoma are observed when the exposure is in the first 2months, and retinopathy during the first 5months [52, 63].Virus may persist for months to years after birth, so appropriate precautions should be taken.
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13.3.3 Diagnosis
The presence of IgM antibodies to rubella in cord blood confirms the diagnosis. Also, viral throat culture may be performed, or serum sampling,for serially rising IgG titers.
13.3.4 Systemic Manifestations
The most common finding is hearing loss,seen in 44% of cases [39]. Other abnormalities include intrauterine growth retardation, heart disease (atrial and ventricular septal defects, and patent ductus arteriosus), microcephaly, and mental retardation. Hepatitis and hepatomegaly may also be seen,and,in the perinatal period, petechiae secondary to thrombocytopenia.
13.3.5 Eye Manifestations
Cornea. The cornea may be edematous either from endotheliopathy (secondary to live virus in the aqueous),or glaucoma [71,72].
Iris and Ciliary Body. These structures may be poorly developed if the virus was contracted early (first trimester),resulting in iris hypoplasia.In addition,a chronic,granulomatous iridocyclitis may persist with focal necrosis and vacuolization of the pigment epithelium of the iris and ciliary body.
Lens. Virus infection during the first trimester effects lens development and results in cataract formation, usually in the form of a nuclear cataract,but may be total.Live virus persists for years and appropriate precautions should be taken during cataract extraction to minimize exposure to cortical material.A robust inflammatory reaction may follow surgery and systemic steroids may be required.
Retina. The classic retinal finding is described as “salt and pepper” retinopathy, and was described in 22% of patients in a large study. (Fig.13.2) [21]. It corresponds to a histopathologic depigmentation of the retinal pigment epithelium without associated inflammation
208 Chapter 13 Eye Manifestations of Intrauterine Infections
Fig.13.2. The right fundus of a 32-year-old Black woman with a history of congenital rubella syndrome. The patient was deaf and mute, and showed some developmental delay. Vision in this eye was 20/25. Salt-and-pepper background retinopathy can be seen throughout the slide but especially in the macular area
Fig.13.3. A light micrograph of hematoxylin-eosin stained retina of a child with congenital rubella syndrome. Between the neuroretina above and the choroid below lies the retinal pigment epithelium (see arrow).It can be seen that the normal palisade of even pigmentation is disrupted. This variability in RPE pigmentation is the cause for the salt-and-pepper appearance in the retinopathy of rubella syndrome
(Fig.13.3).The distribution ofthis finding varies greatly and is associated with a normal ERG.
Glaucoma. Glaucoma is reported in 10% of children with congenital rubella syndrome [71]. The pathogenesis varies from abnormal development of the angle similar to primary congenital glaucoma,to glaucoma secondary to chronic iridocyclitis, to angle closure secondary to a large cataractous lens.
Microphthalmos. Microphthalmos and/or microcornea have been described in 10% of patients [71]. Microphthalmos is often associated with cataract,and it is postulated that it reflects the growth retardation effect ofthe virus on developing tissues paralleling the systemic growth retardation [74].
13.3.6 Treatment
Therapy is supportive.
13.3.7 Prevention
Use of the vaccine RA-27 has had an enormous impact on the incidence of congenital rubella, with the last major outbreak in the United States being in 1964 [3].
13.4 Cytomegalovirus
13.4.1 Agent and Epidemiology
Cytomegalovirus is a member of the herpesvirus group, and was first described in the late nineteenth century as a rare cause of “cytomegalic inclusion disease”of the fetus and newborn [35].It is the cause for the most common intrauterine infection,with reported rates ranging from 0.5% to 2.4% of live births [24]. Infection is usually subclinical. The prevalence of latent infections in young adults varies with
age and geography, increasing with age, and being more prevalent in developing countries [43,67].
13.4.2 Transmission
Prenatal transmission is thought to occur during maternal viremia secondary to a primary infection (most serious damage to the fetus), reinfection,or reactivation of a latent maternal infection [27]. Natal transmission may occur secondary to exposure to genital secretions at the time ofdelivery.Also,neonatal transmission may occur from ingestion of breast milk.
13.4.3 Diagnosis
Specific IgM antibody in the neonate is strong presumptive evidence. Isolation of virus from the infant within the first 3weeks definitively makes the diagnosis,and virus has been recovered from urine, cerebrospinal fluid, saliva, buffy coat, aqueous, biopsy, and postmortem tissue [26].PCR analysis is also promising [64].
13.4.4 Systemic Manifestations
Most neonates with congenital cytomegalovirus infection, 90–95%, are asymptomatic during the neonatal period [67]. Clinical manifestations include intrauterine growth retardation, thrombocytopenic purpura, microcephaly, (periventricular calcifications), hepatosplenomegaly,jaundice,pneumonia,and sensorineural deafness [21].
13.4.5 Eye Manifestations
Anterior Segment. Corneal opacities have been described in pathology specimens [56].Bilateral anterior polar cataracts were seen in 1 of 42 symptomatic patients studied by Coats [16].
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Retina. The retinal disease is a chorioretinitis, resulting in a chorioretinal scar similar to that of toxoplasmosis.Dobbins reported 15% of patients showed retinal disease, and a later study by Coats had 22% ofsymptomatic patients with retinal disease (7% macular and 14% peripheral scars) [16,24].The retinitis usually develops in patients with clinically apparent cytomegalic inclusion disease,but has been reported as the only manifestation of congenital CMV infection.(Fig.13.4) [66].In addition,it has been reported that retinal disease developed several weeks after birth [56]. The histopathology has been reported as “many inclusion bodies in the retina and a few in the choroid, accompanied by extensive chorioretinitis. Accumulation of inclusion bodies in the retina results in focal destruction and gave rise to the development of pseudocolobomas”[51].
Optic Nerve. Optic nerve hypoplasia and optic nerve coloboma have been described in association with cytomegalic inclusion disease [34]. These findings are consistent with the teratogenic effect on the central nervous system seen in this infection,which results in faulty organogenesis.In a large study by Coats,7% of 42 symptomatic patients had bilateral optic atrophy [24].
Other. Cyclopia and anophthalmia have also been reported, and further support the evidence for a teratogenic effect [12,28].
13.4.6 Treatment
Ganciclovir and foscarnet delivered intravenously are being used and studied; however, trials of both show that viruria returns to pretreatment levels after the cessation of the drug [4,62,68].Intravitreal therapy with ganciclovir implants has also been used for the eye disease.
13.4.7 Prevention
Pregnant women who are seronegative should practice good hygiene when they are around young children either at home or in group child-care settings [21].
13.5 Herpes Simplex Virus
13.5.1 Agent and Epidemiology
Herpes simplex virus (HSV) is a double-stranded DNA virus. HSV infections were first described by the Greeks,and Hippocrates used the word “herpes,”which means to creep or crawl to describe the spreading of the lesion [69].There are two types of Herpes simplex virus (HSV), HSV type 1 and type 2.HSV-1 is the oral strain, and is responsible for mouth lesions,eye infections,and encephalitis,while HSV-2 is the genital strain, and produces genital infection [26, 69].The latter is transmitted venereally,the former is not.
13.5.2 Transmission
Of herpes infections seen in the neonatal period,4% are congenital,86% natal,and 10% postnatal [69].Therefore,this is most often a neonatal disease, and not a congenital disease. It is thought that the congenital infection occurs during maternal leukocyte-associated viremia
210 Chapter 13 Eye Manifestations of Intrauterine Infections
Fig.13.4. The left fundus of a 6-month-old female child with congenital cytomegalovirus (demonstrating CMV retinitis).The superior vessels are sheathed
with transplacental transmission. The natal transmission is due to aspiration of infected vaginal secretions on passage through the birth canal. Other possible entry sites include eyes, scalp,skin,and umbilical cord [54,68,69].
13.5.3 Diagnosis
The diagnosis can be made definitively by isolation of the virus from vesicular fluid, nasal secretions,conjunctival secretions,buffy coat of blood, and cerebral spinal fluid of the infant [29].
13.5.4 Systemic Manifestations
Systemic manifestations reported in 30 patients with congenital HSV include low birth weight, small for gestational age,microcephaly,seizures, diffuse brain damage, intracranial calcifications,scars on skin or digits,pneumonitis,and hepatomegaly [38]. Infants with natal or postnatal herpes commonly present 5–15days postnatally and resemble bacterial sepsis: alterations in temperature, lethargy, respiratory distress, anorexia, vomiting, and cyanosis. The overall mortality rate from untreated,neonatal HSV infection is 49% and only 26% of survivors develop normally [26].
13.5.5 Eye Manifestations
Thirteen percent ofneonates with HSV have eye manifestations [26]. It is difficult to separate congenital and neonatal cases in the literature.
Anterior Segment. Conjunctivitis,keratitis,iridocyclitis,iris atrophy,posterior synechiae,and cataract have been described in congenital and neonatal herpes [53].
Retina. Retinitis, chorioretinitis, chorioretinal scarring, and white vitreous masses have been described.(Fig.13.5) [41,53,58].
Optic Nerve. There have been cases of optic neuritis and optic atrophy [41,53].
Microphthalmia. Microcornea and microphthalmia have been described in a patient with associated intrauterine growth retardation and microcephaly,suggesting a teratogenic effect of early intrauterine herpes [41].
13.5.6 Treatment
For disseminated herpes infections,acyclovir is the drug of choice,delivered intravenously at a dose of 30mg/kg per day for 10days to 4weeks [55]. The major side effect is renal toxicity. Vidarabine is also administered as a single IV infusion of 15mg/kg per day over 12h. Hepatic toxicity and bone marrow suppression are potential side effects. Topical antivirals (vidarabine, trifluorothymidine, and idoxuridine) are used to treat the epithelial keratitis along with debridement.
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Fig.13.5. The left fundus of a 13-year-old boy with a diagnosis of congenital herpes simplex virus infection.Centrally,there is a large white gliotic scar overlying the macular area. In the background there are areas of migration of the pigment of the retinal pigment epithelium
13.5.7 Prevention
Perinatal screening and neonatal treatment may be helpful for the neonatal and postnatal forms.
13.6 Lymphocytic Choriomeningitis Virus
This agent is in the “other”category,but will be discussed more extensively because the author feels it is greatly underdiagnosed due to lack of knowledge.
13.6.1 Agent and Epidemiology
Lymphocytic choriomeningitis virus (LCMV) is an arena virus that was discovered in 1933 but not classified until the late 1960s, when it was placed in the newly formed arena virus family of single-stranded RNA viruses with rodent reservoirs [2, 59]. Mus musculus, the common house mouse,is both the natural host and reservoir for the virus,which is transferred vertically within the mouse population by intrauterine infection [57, 59]. A nationwide outbreak in the 1970s provided evidence that pet (Syrian) hamsters may be competent alternative reservoirs [8,20,33,60,65].Infections from house mice are associated with substandard housing, such as trailer parks and inner city dwellings [57].Outbreaks have also been attributed to laboratory mice and hamsters; laboratory workers, especially those handling mice or hamsters, have a higher risk of infection [6,25,37].Transmission is thought to be airborne; from contamination of food by infected mouse urine,feces,and saliva [37] or,possibly,from the bites ofinfected rodents [57].The first case of congenital LCMV in the United States was reported in 1993 [45].
13.6.2 Transmission
Transmission to the fetus is thought to occur during maternal viremia.Most likely,as with the other agents, the earlier in gestation, the more serious the sequelae.
13.6.3 Diagnosis
Although complement fixation (CF) tests for LCMV are widely available, CF antibodies are short-lived; the test is insensitive and should not be utilized. Immunofluorescent antibody (IFA) tests and Western blot assays are sensitive, detect both IgM and IgG antibody,and are available both commercially as well as at the Centers for Disease Control (CDC).Enzyme-linked immunosorbent assay (ELISA) is also a sensitive diagnostic modality,but it is performed only at the CDC.
13.6.4 Systemic Manifestations
A recent publication identified 26 cases of congenital LCMV in the world literature between 1955 and 1996 and summarized the ten cases reported in the United States [73].The most common systemic, neonatal findings among these cases were macrocephaly and microcephaly. A subsequent report summarizing 49 cases in the world literature states that 17 of 19 infants in whom imaging was reported showed hydrocephalus or intracranial calcifications [5]. Evidently, systemic signs suggesting congenital infection are infrequent though neonatal meningitis, hepatosplenomegaly, and congenital heart disease have been reported [5, 50, 73].As development progresses,neurologic abnormalities become more obvious, including cerebral palsy, mental retardation, and seizures [5]. There have been two cases reported in which the eye findings were the only manifestation [11].
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13.6.5 Eye Manifestations
The eye findings of LCMV described in the US literature (17 cases), 14 with eye findings described (28 eyes), are listed in Table13.2 [50]. The most common finding is chorioretinal scars
in the periphery (20 eyes) (Fig.13.6). Macular chorioretinal scars were the second most prevalent findings (ten eyes) and in five of these eyes there was also peripheral scarring. Optic atrophy was seen bilaterally in three patients,but always in association with extensive chorioretinal scars and therefore it may be secondary to the scarring.Nystagmus was present in three cases, but that along with esotropia and exotropia, each in one patient,is probably secondary to the visual loss due to the chorioretinal scarring.The cataract and microphthalmia were seen in the same eye.
13.6.6 Treatment
Treatment is supportive.
13.6.7 Prevention
Pregnant women should be informed to avoid mice and hamsters.
13.7 Others
13.7.1 Treponema Pallidum
The eye manifestations of congenital syphilis include corneal opacities,scarring from uveitis, cataract, glaucoma, pigmentary retinopathy (salt and pepper),and optic atrophy [46].
13.7.2 Varicella–Zoster Virus
The ocular manifestations described in the congenital varicella syndrome include chorioretinitis, both atrophy and hypoplasia of the optic nerve, congenital cataract, and Horner’s syndrome [44].
13.7 Others 213
Fig.13.6. The left eye of a 3-year-old child with a diagnosis of congenital lymphocytic choriomeningitis virus (LCMV).A large chorioretinal scar is visible filling the nasal retina.There are also some irregularities ofthe retinal pigment epithelium just nasal to the disc at the 9 and 11 o’clock positions.There appears to be some straightening of the nasal arcade vessels secondary to the scarring
Table13.2. Eye findings described in congenital LCMV
Chorioretinal scars Generalized 71% (20) Macula 36% (10) Optic atrophy 21% (6) Nystagmus 10% (3) Esotropia 4% (1) Microphthalmos 4% (1) Cataract 4% (1) Retinitis 4% (1)
Total number of eyes described in the literature is 28. Each eye may have more than one finding,therefore the percentages do not add up to 100%
13.7.3 Human Immunodeficiency Virus
The incidence of children with congenital HIV is decreasing dramatically with the advent of new drugs.Both CMV retinitis and toxoplasmic chorioretinitis have been described in this patient population [7,9].
13.7.4 Epstein–Barr Virus
Congenital Epstein–Barr virus infection (infectious mononucleosis) has been reported associated with congenital cataracts in two of five cases [29]. These agents produce a relatively mild illness in the mother and are transmitted transplacentally to the fetus and have both a direct toxic and a teratogenic effect.Often,because of immunologic immaturity, the infant is unable to eliminate the organisms and immune tolerance and chronic infection results.
13.8 West Nile Virus
13.8.1 Agent and Epidemiology
West Nile virus (WNV) was first isolated from a febrile patient in the West Nile district of Uganda in 1937.From 1937 to the early 1990s,human outbreaks,manifesting as mild febrile illnesses, were rarely reported in Israel and Africa.Since 1996, there have been outbreaks involving thousands of people in Romania,Russia,Israel, and the United States and Canada. More than 4,000 people were affected in the Ohio and Mississippi River basins in 2002. Eighty-five percent of human infections occur in August and September, consistent with the bird-mosquito-bird cycle. Increased age is a risk factor for mortality. West Nile virus is a single-stranded RNA flavivirus belonging to the Japanese encephalitis virus antigenic complex.This complex con
tains several viruses that cause encephalitis in humans: St. Louis encephalitis virus in the Americas, Japanese encephalitis virus in East Asia, and Murray Valley encephalitis virus and Kunjin virus in Australia.Two lineages ofWNV exist. Only lineage 1 viruses cause human disease.The virus has minimally evolved genetically since being isolated in 1999 [30].
13.8.2 Transmission
WNV is transmitted in a bird-mosquito-bird cycle with passerine birds serving as the primary host and mosquitoes from the genus Culexserving as the primary vectors.The virus, however, has been isolated from 29 mosquito species in the United States alone [13, 30]. Almost all human infections with WNV have been caused by mosquito bites. However, in 2002, there were several cases reporting transmission via other modalities, including one baby transplacentally, one baby via breast milk, two laboratory workers via percutaneous inoculation, four recipients of organs from a single donor,and 23 recipients of transfused platelets, red blood cells,or fresh frozen plasma [30].
13.8.3 Diagnosis
Diagnosis is made by detecting the IgM antibody in serum or CSF using the IgM antibodycapture enzyme-linked immunosorbent assay (MAC-ELISA). Of patients presenting with meningoencephalitis, 90% will demonstrate IgM antibody in the CSF within 8days of onset of clinical symptoms. Because IgM antibody may persist in serum for more than 500days,a fourfold or higher increase in WNV-specific neutralizing antibody titer in serum samples is considered confirmatory of acute infection. A set of other flaviviruses should be included in the assay for comparison [13].
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13.8.4 Systemic and Eye Manifestations
There has only been one case report oftransplacental transmission.This infant presented with bilateral chorioretinitis, clear vitreous, and severe neurologic impairment [1,14,30].
13.8.5 Treatment
All patients should be hospitalized for observation and supportive care,and to rule out treatable CNS conditions. There is no vaccine. Antiviral agents, including ribavirin, interferon alpha, and human immunoglobulin, have not proven effective [13,14].
13.8.6 Prevention
Pregnant women should avoid mosquito bites by wearing protective clothing and using repellants containing N,N-diethyl-m-toluamide (DEET) [14].

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